What's better than canned air?

From: Joe <rigdonj_at_cfl.rr.com>
Date: Thu Jan 23 08:19:00 2003

At 08:56 PM 1/21/03 GMT, you wrote:
>On Jan 21, 13:01, chris wrote:
>
>> The tank is good to about 200 PSI, and comes with a regulator assembly
>> and hose. The compressor is good to 250 PSI so it fills it nicely.
>>
>> I added a coiled hose and blow gun attachment, and the system works quite
>> well. The compressor is a tad loud, so sometimes I walk away and close my
>> office door when it is filling (the tank does NOT have a blow off valve,
>> so I can't walk away for too long or I risk overfilling, so mostly I just
>> go deaf when it fills).
>
>I was wondering about excess pressure the other day. I thought about a
>pressure switch to shut off the motor, but they seem to be quite expensive.
> Or am I just looking in the wrong places? Does anyone know where I could
>get a pressure switch suitable for about 120 psi, cheaply?

   I don't know about the UK but such switches are readily available in the US. They're used for controlling the pumps on individual household water wells. You can find them in any decent hardware store and they sell for about $10. They're usually marked 20-40 or 40-60. The first number is the pressure (in PSIG) at which the contacts close and the second number is the pressure at which they open*. However under the cover you will find two adjusting screws that you alter both settings. My Sears compressor came standard with that type switch. BTW the contacts are 4PST but they're usually wired up as DPST and are rated for at least 230 VAC and plenty of current since they're designed to control motors with large inductive loads. IIRC the pipe connection is 3/8" NPT.

 *These switches are purposely designed to open in the pressure gets too low. That's to prevent the pump from running continuesly if the pipe should break and all pressure is lost. I'm sure that this feature can be adjusted out.

     Joe
Received on Thu Jan 23 2003 - 08:19:00 GMT